/**
 * 图像验证码
 */
module.exports = class Mcaptcha {
    constructor(options) {
        this.options = options;
        this.fontSize = options.height * 3 / 4;
        this.offsetTop = options.height * 0.5;
        this.ctx = wx.createCanvasContext(this.options.el);
        this.refresh(this.options.code);
    }
    refresh(code) {
        this.options.code = code + '';
        this.ctx.clearRect(0, 0, this.options.width, this.options.height);
        this.ctx.restore();
        this.ctx.setTextBaseline("middle");
        this.ctx.setFillStyle(this.randomColor(180, 240));
        this.ctx.fillRect(0, 0, this.options.width, this.options.height);
        let arr = this.options.code.split('');
        if (arr.length === 0) {
            arr = ['e', 'r', 'r', 'o', 'r'];
        };
        let offsetLeft = this.options.width * 0.6 / (arr.length - 1);
        let marginLeft = this.options.width * 0.2;
        arr.forEach((item, index) => {
            this.ctx.setFillStyle(this.randomColor(0, 180));
            let size = this.randomNum(24, this.fontSize);
            this.ctx.setFontSize(size);
            let dis = offsetLeft * index + marginLeft - size * 0.3;
            let deg = this.randomNum(-30, 30);
            this.ctx.translate(dis, this.offsetTop);
            this.ctx.rotate(deg * Math.PI / 180);
            this.ctx.fillText(item, 0, 0);
            this.ctx.rotate(-deg * Math.PI / 180);
            this.ctx.translate(-dis, -this.offsetTop);
        })
        this.ctx.draw();
    }
    randomNum(min, max) {
        return Math.floor(Math.random() * (max - min) + min);
    }
    randomColor(min, max) {
        let r = this.randomNum(min, max);
        let g = this.randomNum(min, max);
        let b = this.randomNum(min, max);
        return "rgb(" + r + "," + g + "," + b + ")";
    }
}